Pathophysiological remodeling of the enteric neuromuscular compartment in experimental spinal cord injury

摘要 脊髓损伤（SCI）最明显的物理影响是运动控制的丧失 和感觉的能力。然而，神经源性肠是最普遍和临床上最常见的肠梗阻之一。 公认的与SCI相关的合并症，表现为结肠传输减少，便秘， 排泄协同失调和溢出性尿失禁。结肠失调被认为是一种终身的身体疾病， 严重影响患者的生活质量。SCI与 储存和排泄的缺陷促进了一种内在的倾向，即集中于脊髓上调节的丧失 脊髓的躯体和自主神经回路。然而，胃肠道是独特的，因为它有自己的 广泛的内在神经系统，肠神经系统（ENS），并具有功能的准， 自主地。正常的结肠运输需要ENS和细胞合胞体的维持， 平滑肌收缩以调节内在反射和协调肠道活动。虽然函数 的ENS被认为是保留后SCI，反射结肠运输的中断表明， 否则虽然神经源性肠的病理生理学仍有待了解，但针对GI的研究 运动障碍提示肠神经元、Cajal间质细胞（ICC）和成纤维细胞样细胞的丢失 (FLC)可能是大多数这些疾病的根本原因。这些细胞形成神经肌肉 所有平滑肌活动都是通过这个界面调节的。在这个建议中，我们将使用一个动物模型， T3-SCI结合分子和细胞技术以及在体神经生理学记录， 目的是确定导致肠神经系统介导的结肠功能丧失的机制， SCI.我们的总体假设是脊髓损伤通过减少肠蠕动而引起结肠动力障碍。 神经系统调节我们将证明，活性氧（ROS）水平升高， 在肠道神经肌肉回路丧失之前，ROS清除剂将拯救这些细胞。基于 根据我们的初步观察，我们将检验以下假设：1）SCI降低神经肌肉功能， SCI后结肠平滑肌内的传导; 2）SCI引起ENS神经元、ICC和 FLC（结肠合胞体的神经肌肉重塑）; 3）SCI引起抗氧化防御受损 通过评估结肠内ROS水平的升高和 血红素加氧酶1（HO 1）是一种重要的抗氧化分子。我们最初的预期是胆碱能兴奋性 连接电位和抑制性（氮能和嘌呤能）连接电位将降低，因此 表明引起结肠运输抑制的肠神经病。这些收敛的测试 中心假说将为SCI后发生的炎症机制提供有价值的见解， 提供治疗策略以减少这种改变，从而改善结肠炎的功能结果， 运动障碍

ABSTRACT The striking physical effects of spinal cord injury (SCI) are most obviously observed as a loss of motor control and sensation below the level of injury. However, neurogenic bowel is one of the most prevalent and clinically recognized comorbidities associated with SCI and is manifested as diminished colonic transit, constipation, evacuation dyssynergy, and overflow incontinence. Colonic dysregulation is recognized as a lifelong physical and psychological challenge for SCI patients and gravely impacts quality of life. The association of SCI with storage and evacuation deficits promotes an inherent tendency to focus upon the loss of supraspinal regulation of somatic and autonomic circuitry of the spinal cord. However, the GI tract is unique in that it has its own extensive intrinsic nervous system, the enteric nervous system (ENS), and has the ability to function quasi- autonomously. Normal colonic transit requires maintenance of the ENS and a syncytium of cells regulating contraction of the smooth muscle to modulate intrinsic reflexes and coordinate gut activity. While the function of the ENS is presumed to be preserved following SCI, the disruption of reflex colonic transit suggests otherwise. While the pathophysiology of neurogenic bowel remains to be understood, studies focusing on GI motility disorders suggest that a loss of enteric neurons, interstitial cells of Cajal (ICC) and fibroblast-like cells (FLC) may be an underlying cause for the majority of these disorders. These cells form the neuromuscular interface through which all smooth muscle activity is regulated. In this proposal we will use an animal model of T3-SCI combined with molecular and cellular techniques as well as in vivo neurophysiological recordings in an aim to define the mechanisms resulting in the loss of enteric nervous system-mediated colonic function post- SCI. Our overarching hypothesis is that spinal cord injury induces colonic dysmotility by reducing the enteric nervous system regulation. We will demonstrate that elevated levels of reactive oxygen species (ROS) precedes the loss of enteric neuromuscular circuits and that ROS scavengers will rescue these cells. Based upon our preliminary observations, we will test the hypothesis that 1) SCI decreases neuromuscular transmission within the colonic smooth muscle after SCI; 2) SCI provokes the loss of ENS neurons, ICC and FLC (neuromuscular remodeling of the colonic syncytium); and 3) SCI provokes impaired anti-oxidant defense of the proximal and distal colon by evaluating elevated ROS levels within the colon and diminished levels of heme oxygenase 1 (HO1), a key anti-oxidant molecule. Our initial expectation is that cholinergic excitatory junction potentials and inhibitory (nitrergic and purinergic) junction potentials will be reduced, thus demonstrating an enteric neuropathy provoking inhibition of colonic transit. These convergent tests of the central hypothesis will provide valuable insight into the inflammatory mechanisms which occur post-SCI and offer therapeutic strategies to reduce such alterations, thereby improving the functional outcome of colonic dysmotility.